Aerosol-generating article comprising a hollow tube segment comprising polyhydroxyalkanoate

ABSTRACT

An aerosol-generating article is provided for producing an inhalable aerosol upon heating, the aerosol-generating article including: a rod of aerosol-generating substrate, the aerosol-generating substrate including at least 12 percent by weight of an aerosol former, and the rod having a length of from 5 millimetres to 50 millimetres; and a hollow tube segment with a support element and including fibrous filtration material, the hollow tube segment disposed immediately downstream of the rod and in longitudinal alignment with the rod, in which the fibrous filtration material includes fibres including a polyhydroxyalkanoate (PHA) polymer or copolymer, and in which the hollow tube segment includes at least about 25 percent by weight of the PHA polymer or copolymer. A system including an aerosol-generating device and the aerosol-generating article is also provided.

The present invention relates to a hollow tube segment for use in anaerosol-generating article and to an aerosol-generating articlecomprising the hollow tube segment. The present invention furtherrelates to an aerosol-generating system comprising an aerosol-generatingdevice and one such aerosol-generating article.

Conventional aerosol-generating articles, such as filter cigarettes,typically comprise a cylindrical rod of tobacco cut filler surrounded bya paper wrapper and a cylindrical filter axially aligned, most often inan abutting end-to-end relationship, with the wrapped tobacco rod. Thecylindrical filter typically comprises one or more plugs of a fibrousfiltration material, such as cellulose acetate tow, circumscribed by apaper plug wrap. Conventionally, the wrapped tobacco rod and the filterare joined by a band of tipping wrapper, normally formed of an opaquepaper material that circumscribes the entire length of the filter and anadjacent portion of the wrapped tobacco rod.

Aerosol-generating articles in which an aerosol-generating substrate,such as a tobacco-containing substrate, is heated rather than combusted,are also known in the art. Typically in such articles an aerosol isgenerated by the transfer of heat from a heat source to a physicallyseparate aerosol-generating substrate or material.

By way of example, aerosol-generating articles have been proposedwherein an aerosol is generated by electrical heating of anaerosol-generating substrate. A number of prior art documents discloseaerosol-generating devices for consuming aerosol-generating articles.Such devices include, for example, electrically heatedaerosol-generating devices in which an aerosol is generated by thetransfer of heat from one or more electrical heater elements of theaerosol-generating device to the aerosol-generating substrate of aheated aerosol-generating article. As another example,aerosol-generating articles are also known wherein an aerosol isgenerated by the transfer of heat from a combustible fuel element orheat source to an aerosol-generating substrate. The combustible fuelelement or heat source may be located in contact with, within, around,or downstream of the aerosol-generating substrate.

During use of one such aerosol-generating article, volatile compoundsare released from the aerosol-generating substrate by heat transfer andare entrained in air drawn through the aerosol-generating article. Asthe released compounds cool, they condense to form an aerosol.

Typically, aerosol-generating articles of the types described mayinclude a mouthpiece comprising a filter segment formed of porousfiltration material such as cellulose acetate. In some knownaerosol-generating articles a hollow tubular segment formed of afiltration material such as cellulose acetate is provided at a locationbetween the aerosol-generating substrate and the mouth end of thearticle to impart structural strength to the article.

A number of aerosol-generating articles have also been described thatcomprise a hollow tube segment formed of fibrous filtration material. Byway of example, aerosol-generating articles have been disclosed that, inaddition to the rod of aerosol-generating substrate, comprise a supportelement in the form of a hollow acetate tube. In a particularembodiment, one such aerosol-generating article comprises, in linearsequential arrangement, a rod of aerosol-generating substrate, a hollowacetate tube located immediately downstream of the aerosol-generatingsubstrate, an aerosol-cooling element located downstream of the hollowacetate tube, and an outer wrapper circumscribing the rod, the hollowacetate tube and the aerosol-cooling element.

Further, conventional aerosol-generating articles have been proposedwherein the filter comprises a hollow tube segment formed of fibrousfiltration material, preferably in combination and in axial alignmentwith another non-hollow segment formed of fibrous filtration material.By way of example, filter cigarettes have been disclosed wherein onesuch hollow tube segment is arranged at the mouth end of the filtercigarette, such that the cavity internally defined by the hollow tubesegment is open to the outer environment. Filter cigarettes have alsobeen disclosed wherein one such hollow tube segment is arranged betweennon-hollow segments formed of fibrous filtration material. The cavityinternally defined by the hollow tube segment and delimited at its endsby the two non-hollow segments may contain an aerosol-alteringsubstance, such as a sorbent material, or a frangible flavour capsule,etc.

After an aerosol-generating article has been consumed and discarded, itmay be desirable for any component of the article comprising filtrationmaterial to break down as quickly as possible. However, celluloseacetate, and many other commonly used filtration materials are nothighly biodegradable. However, alternative dispersible or biodegradablematerials are often not able to provide an acceptable filtrationefficiency and smoking experience for the consumer. Furthermore, manyknown dispersible and degradable materials are unsuitable for use in theexisting manufacturing processes, and would require too significant amodification of the existing methods and equipment to make their usecommercially feasible.

Further, cellulose acetate has been found to provide a relatively highlevel of adsorption and trapping of water from the mainstream smoke whenused in conventional smoking articles. The mainstream smoke delivered tothe consumer therefore has a significantly reduced moisture content andmay, under certain conditions, be perceived as undesirably ‘dry’. Thismay have an adverse effect on the overall smoking experience.

Thus, it would be desirable to provide a novel and improvedaerosol-generating article that has enhanced biodegradation propertiescompared to known articles including conventional filtration materialssuch as cellulose acetate. It would also be desirable to provide a noveland improved aerosol-generating article that provides an acceptablesmoking experience to the consumer, in particular, one that is capableof reducing the ‘dry’ smoke effect that is often found with articlescomprising cellulose acetate as the filtration material.

It would be desirable to provide one such aerosol-generating articlewherein the resistance to draw (RTD) of a filtration material segmentcan be adjusted so as to achieve an acceptable RTD of the article as awhole. Further, it would be desirable to provide such anaerosol-generating article that can effectively be produced in anautomated, high-speed manufacturing process without requiring majormodifications of existing equipment.

The present disclosure relates to an aerosol-generating article forproducing an inhalable aerosol upon heating. The aerosol-generatingarticle may comprise a rod of aerosol-generating substrate and a hollowtube segment comprising fibrous filtration material. The hollow tubesegment may be arranged in longitudinal alignment with the rod. Thefibrous filtration material may comprise fibres comprising apolyhydroxyalkanoate (PHA) polymer or copolymer material.

Further, the present disclosure relates to a hollow tube segment for usein an aerosol-generating article. The hollow tube segment may be formedof fibrous filtration material. The fibrous filtration material maycomprise fibres comprising a polyhydroxyalkanoate (PHA) polymer orcopolymer material.

In addition, the present disclosure relates to a system comprising anaerosol-generating device and an aerosol-generating article for use withthe aerosol-generating device. The aerosol-generating article maycomprise a rod of aerosol-generating substrate and a hollow tube segmentcomprising fibrous filtration material. In the aerosol-generating devicethe hollow tube segment may be arranged in longitudinal alignment withthe rod. The fibrous filtration material may comprise fibres comprisinga polyhydroxyalkanoate (PHA) polymer or copolymer.

According to the present invention, there is provided anaerosol-generating article for producing an inhalable aerosol uponheating, the aerosol-generating article comprising: a rod ofaerosol-generating substrate; a hollow tube segment comprising fibrousfiltration material, the hollow tube segment arranged in longitudinalalignment with the rod; wherein the fibrous filtration materialcomprises fibres comprising a polyhydroxyalkanoate (PHA) polymer orcopolymer.

The term “aerosol-generating article” is used herein with reference tothe invention to describe an article wherein an aerosol-generatingsubstrate is heated to produce and deliver an aerosol to a consumer. Asused herein, the term “aerosol-generating substrate” denotes a substratecapable of releasing volatile compounds upon heating to generate anaerosol.

A conventional cigarette is lit when a user applies a flame to one endof the cigarette and draws air through the other end. The localised heatprovided by the flame and the oxygen in the air drawn through thecigarette causes the end of the cigarette to ignite, and the resultingcombustion generates an inhalable smoke. By contrast, in heatedaerosol-generating articles, an aerosol is generated by heating aflavour generating substrate, such as, for example, a tobacco-basedsubstrate or a substrate containing an aerosol-former and a flavouring.Known heated aerosol-generating articles include, for example,electrically heated aerosol-generating articles and aerosol-generatingarticles in which an aerosol is generated by the transfer of heat from acombustible fuel element or heat source to a physically separate aerosolforming material.

As used herein, the term “longitudinal” refers to the directioncorresponding to the main longitudinal axis of the aerosol-generatingarticle, which extends between the upstream and downstream ends of theaerosol-generating article. As used herein, the terms “upstream” and“downstream” describe the relative positions of elements, or portions ofelements, of the aerosol-generating article in relation to the directionin which the aerosol is transported through the aerosol-generatingarticle during use.

As described briefly above, in contrast with existing aerosol-generatingarticles, an article in accordance with the present invention comprisesa hollow tube segment comprising fibrous filtration material, whereinthe fibrous filtration material comprises fibres comprising apolyhydroxyalkanoate (PHA) polymer or copolymer.

Thus, in the hollow tube segment of an aerosol-generating article inaccordance with the invention a PHA polymer or copolymer accounts for atleast a portion of the fibrous filtration material. This means that theremainder of the fibrous filtration material may comprise a materialother than a PHA polymer or copolymer. Further, this means that othercomponents of the hollow tube segment—such as, for example, a plugwrapper circumscribing the fibrous filtration material, or an insert, anon-cuttable object, such as a flow restrictor or an additive deliverymaterial, such as a breakable capsule, which may be provided at alocation along the hollow tube segment may comprise a material otherthan a PHA polymer or copolymer.

Because fibres containing a PHA polymer or copolymer (in the following,also referred to as “PHA fibres”) have a lower hydrophilicity comparedwith fibres of other filtration materials, such as cellulose acetate, ofan equivalent weight, in aerosol-generating articles in accordance withthe present invention the hollow tube segment has been found to have asignificantly lower tendency to absorb water/steam. As a result, inthose embodiments when the hollow tube segment is used as a component ofa multi-segment filter in a conventional smoking article, the level ofwater in the mainstream smoke can advantageously be maintained at ahigher level. This directly addresses the issue of “dry smoke” oftenencountered with conventional smoking articles, and provides an improvedsmoking experience for the consumer.

As PHA fibres have a much higher level of biodegradability compared withfibres of other filtration materials, such as cellulose acetate,articles in accordance with the present invention are more biodegradableas a whole. At the same time, as PHA fibres are obtained by means of anatural, fermentation process, aerosol-generating articles in accordancewith the present invention also provide improved sustainability for theproduction process. Besides, a hollow tube segment has a greater exposedsurface area compared with a cylindrical plug, and this may also furtherfavour biodegradation.

By adjusting parameters such as the denier per filament, total denier,cross sectional shape, etc. it is possible to adjust the RTD of thefilter segment to desirable ranges for any given filter length or filterdesign.

The term “denier per filament” (dpf) corresponds to the weight in gramsof a single fibre or filament having a length of 9000 metres. In thepresent invention, the value of dpf therefore gives an indication of thethickness of each of the individual PHA fibres within the filtersegment. The denier per filament is expressed in units of denier, where1 denier corresponds to 1 gram per 9000 metres.

The “total denier” of the filtration material defines the total weightin grams of 9000 metres of the combined fibres forming the filtrationmaterial. The total denier for the filter segment therefore correspondsto the denier per filament multiplied by the total number of fibres inthe filter segment.

In addition, the overall weight of the hollow tube segment may beadvantageously controlled, and this may also contribute to help withbiodegradation of the hollow tube segment and of the aerosol-generatingarticle as a whole.

PHA properties also lead to good filter hardness, which can be furtherenhanced by circumscribing the hollow tube segment with a stiff plugwrap.

Aerosol-generating articles in accordance with the present inventioncomprise a rod of aerosol-generating substrate.

The rod of aerosol-generating substrate may be produced using randomlyoriented shreds, strands, or strips of tobacco material. As analternative, as has been proposed, for example in international patentapplication WO-A-2012/164009, the rod of aerosol-generating substratemay be formed from one or more gathered sheets of tobacco material.Alternative rods for aerosol-generating articles have also been proposedthat are formed from strands of homogenised tobacco material, which maybe formed by casting, rolling, calendering or extruding a mixturecomprising particulate tobacco and at least one aerosol former to form asheet of homogenised tobacco material. Further, a rod ofaerosol-generating substrate may be formed from strands of homogenisedtobacco material obtained by extruding a mixture comprising particulatetobacco and at least one aerosol former to form continuous lengths ofhomogenised tobacco material.

The rod of aerosol generating substrate preferably has an externaldiameter that is approximately equal to the external diameter of theaerosol generating article.

Preferably, the rod of aerosol generating substrate has an externaldiameter of at least 5 millimetres. The rod of aerosol generatingsubstrate may have an external diameter of between about 5 millimetresand about 12 millimetres, for example of between about 5 millimetres andabout 10 millimetres or of between about 6 millimetres and about 8millimetres. In a preferred embodiment, the rod of aerosol generatingsubstrate has an external diameter of 7.2 millimetres, to within 10percent.

The rod of aerosol generating substrate may have a length of betweenabout 5 millimetres and about 100 mm. Preferably, the rod of aerosolgenerating substrate has a length of at least about 5 millimetres, morepreferably at least about 7 millimetres. In addition, or as analternative, the rod of aerosol generating substrate preferably has alength of less than about 80 millimetres, more preferably less thanabout 65 millimetres, even more preferably less than about 50millimetres. In particularly preferred embodiments, the rod of aerosolgenerating substrate has a length of less than about 35 millimetres,more preferably less than 25 millimetres, even more preferably less thanabout 20 millimetres. In one embodiment, the rod of aerosol generatingsubstrate may have a length of about 10 millimetres. In a preferredembodiment, the rod of aerosol generating substrate has a length ofabout 12 millimetres.

Preferably, the rod of aerosol generating substrate has a substantiallyuniform cross-section along the length of the rod. Particularlypreferably, the rod of aerosol generating substrate has a substantiallycircular cross-section.

In preferred embodiments, the aerosol-generating substrate comprises oneor more gathered sheets of homogenised tobacco material. Preferably theone or more sheets of homogenised tobacco material are textured. As usedherein, the term ‘textured sheet’ denotes a sheet that has been crimped,embossed, debossed, perforated or otherwise deformed. Textured sheets ofhomogenised tobacco material for use in the invention may comprise aplurality of spaced-apart indentations, protrusions, perforations or acombination thereof. According to a particularly preferred embodiment ofthe invention, the rod of aerosol-generating substrate comprises agathered crimped sheet of homogenised tobacco material circumscribed bya wrapper.

As used herein, the term ‘crimped sheet’ is intended to be synonymouswith the term ‘creped sheet’ and denotes a sheet having a plurality ofsubstantially parallel ridges or corrugations. Preferably, the crimpedsheet of homogenised tobacco material has a plurality of ridges orcorrugations substantially parallel to the cylindrical axis of the rodaccording to the invention. This advantageously facilitates gathering ofthe crimped sheet of homogenised tobacco material to form the rod.However, it will be appreciated that crimped sheets of homogenisedtobacco material for use in the invention may alternatively or inaddition have a plurality of substantially parallel ridges orcorrugations disposed at an acute or obtuse angle to the cylindricalaxis of the rod. In certain embodiments, sheets of homogenised tobaccomaterial for use in the rod of the article of the invention may besubstantially evenly textured over substantially their entire surface.For example, crimped sheets of homogenised tobacco material for use inthe manufacture of a rod for use in an aerosol-generating article inaccordance with the invention may comprise a plurality of substantiallyparallel ridges or corrugations that are substantially evenlyspaced-apart across the width of the sheet.

Sheets or webs of homogenised tobacco material for use in the inventionmay have a tobacco content of at least about 40 percent by weight on adry weight basis, more preferably of at least about 60 percent by weighton a dry weight basis, more preferably or at least about 70 percent byweight on a dry basis and most preferably at least about 90 percent byweight on a dry weight basis.

Sheets or webs of homogenised tobacco material for use in theaerosol-generating substrate may comprise one or more intrinsic binders,that is tobacco endogenous binders, one or more extrinsic binders, thatis tobacco exogenous binders, or a combination thereof to helpagglomerate the particulate tobacco. Alternatively, or in addition,sheets of homogenised tobacco material for use in the aerosol-generatingsubstrate may comprise other additives including, but not limited to,tobacco and non-tobacco fibres, aerosol-formers, humectants,plasticisers, flavourants, fillers, aqueous and non-aqueous solvents andcombinations thereof.

Suitable extrinsic binders for inclusion in sheets or webs ofhomogenised tobacco material for use in the aerosol-generating substrateare known in the art and include, but are not limited to: gums such as,for example, guar gum, xanthan gum, arabic gum and locust bean gum;cellulosic binders such as, for example, hydroxypropyl cellulose,carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose andethyl cellulose; polysaccharides such as, for example, starches, organicacids, such as alginic acid, conjugate base salts of organic acids, suchas sodium-alginate, agar and pectins; and combinations thereof.

Suitable non-tobacco fibres for inclusion in sheets or webs ofhomogenised tobacco material for use in the aerosol-generating substrateare known in the art and include, but are not limited to: cellulosefibres; soft-wood fibres; hard-wood fibres; jute fibres and combinationsthereof. Prior to inclusion in sheets of homogenised tobacco materialfor use in the aerosol-generating substrate, non-tobacco fibres may betreated by suitable processes known in the art including, but notlimited to: mechanical pulping; refining; chemical pulping; bleaching;sulphate pulping; and combinations thereof.

Substrates for heated aerosol-generating articles typically comprise an“aerosol former”, that is, a compound or mixture of compounds that, inuse, facilitates formation of the aerosol, and that preferably issubstantially resistant to thermal degradation at the operatingtemperature of the aerosol-generating article. Examples of suitableaerosol-formers include: polyhydric alcohols, such as propylene glycol,triethylene glycol, 1,3-butanediol and glycerin; esters of polyhydricalcohols, such as glycerol mono-, di- or triacetate; and aliphaticesters of mono-, di- or polycarboxylic acids, such as dimethyldodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formersare polyhydric alcohols or mixtures thereof, such as propylene glycol,triethylene glycol, 1,3-butanediol and, most preferred, glycerine.

Preferably, the aerosol-generating substrate comprises at least 10percent by weight of an aerosol former, more preferably at least 12percent by weight of an aerosol former, more preferably at least about15 percent by weight of an aerosol former. Alternatively or in addition,the aerosol-generating substrate preferably comprises no more than 30percent by weight of an aerosol former, more preferably no more thanabout 25 percent by weight of an aerosol former, more preferably no morethan about 20 percent by weight of an aerosol former. For example, theaerosol-generating substrate may comprise between about 10 percent andabout 30 percent by weight of an aerosol former, or between about 12percent and about 25 percent by weight of an aerosol former, or betweenabout 15 percent and about 20 percent by weight of an aerosol former. Ina particularly preferred embodiment, the aerosol-generating substratecomprises around 18 percent by weight of an aerosol former.

In aerosol-generating articles in accordance with the present invention,the filter segment is formed of fibrous filtration material comprisingfibres comprising a polyhydroxyalkanoate (PHA) polymer or copolymer.Preferably, the fibrous filtration material comprises at least about 85percent by weight of fibres comprising a polyhydroxyalkanoate (PHA)polymer or copolymer.

PHAs are a family of polyhydroxyesters of 3-, 4-, 5- and6-hydroxyalkanoic acids, which are produced by a variety of bacterialspecies under nutrient-limiting conditions with excess carbon and arefound as discrete cytoplasmic inclusions in bacterial cells. Due totheir excellent biocompatibility, PHAs have been proposed for use in awide variety of biomedical applications, including drug delivery systemsand tissue engineering scaffolds.

A PHA molecule is typically made up of 600 to 35,000 (R)-hydroxy fattyacid monomer units. Depending on the total number of carbon atoms withina PHA monomer, PHA can be classified as either short-chain length PHA(scl-PHA; 3 to 5 carbon atoms), medium-chain length PHA (mcl-PHA; 6 to14 carbon atoms), or long-chain length PHA (lcl-PHA; 15 or more carbonatoms).

The first and most prevalent PHA is poly(β-hydroxybutyrate) (PHB). Thenext member of the PHA family, having a pendant ethyl group, ispoly(3-hydroxyvalerate) or PHV. Having an ethyl group (HV unit) insteadof the methyl group of PHB gives PHV more flexibility and lesscrystallinity than PHB.

Preferably, in an aerosol-generating article in accordance with theinvention the hollow tube segment comprises at least about 25 percent byweight of a PHA polymer or copolymer. More preferably, the hollow tubesegment comprises at least about 50 percent by weight of a PHA polymeror copolymer. Even more preferably, the hollow tube segment comprises atleast about 60 percent by weight of a PHA polymer or copolymer. Inparticularly preferred embodiments, the hollow tube segment comprises atleast about 70 percent by weight of a PHA polymer or copolymer or evenat least about 80 percent by weight of a PHA polymer or copolymer. Insome highly preferred embodiments, the hollow tube segment comprises atleast about 85 percent by weight of a PHA polymer or copolymer. Morepreferably, the PHA polymer or copolymer is one or more ofpolyhydroxypropionate, polyhydroxyvalerate, polyhydroxybutyrate,polyhydroxyhexanoate and polyhydroxyoctanoate. In a particularlypreferred embodiment, the PHA compound is poly(3-hydroxybutyrate).

Even more preferably, the hollow tube segment comprises at least about90 percent by weight of a PHA polymer or copolymer. Without wishing tobe bound by theory, it is understood that higher contents of PHA in thehollow tube segment are generally associated with an improvedbiodegradability of the hollow tube segment and of theaerosol-generating article as a whole.

More preferably, the fibrous filtration material comprises at leastabout 91 percent by weight of a PHA polymer or copolymer or at leastabout 92 percent by weight of a PHA polymer or copolymer or at leastabout 93 percent by weight of a PHA polymer or copolymer or at leastabout 94 percent by weight of a PHA polymer or copolymer. In someparticularly preferred embodiments, the fibrous filtration materialcomprises at least about 95 percent by weight of a PHA polymer orcopolymer.

The remainder of the fibres within the PHA filter segment may compriseany suitable material. Suitable fibrous materials would be known to theskilled person and include but are not limited to polylactic acid (PLA)and cellulose acetate.

In some embodiments, the fibrous filtration material of the hollow tubesegment may comprise some cellulose acetate. Without wishing to be boundby theory, it is understood that a certain amount of cellulose acetatein the hollow tube segment may impart desirable filtration propertiesand mechanical properties to the hollow tube segment as well asfacilitating manufacture of the hollow tube segment.

In certain embodiments, the fibrous filtration material of the hollowtube segment comprises at least about 5 percent by weight of celluloseacetate. By way of example, the fibrous filtration material may compriseat least about 6 percent by weight of cellulose acetate or at leastabout 7 percent by weight of cellulose acetate or at least about 8percent by weight of cellulose acetate or at least about 9 percent byweight of cellulose acetate. In some embodiments, the fibrous filtrationmaterial comprises at least about 10 percent by weight of celluloseacetate.

In aerosol-generating articles in accordance with the present invention,the fibrous filtration material preferably comprises less than about 15percent by weight of cellulose acetate.

In some embodiments, the fibrous filtration material of the hollow tubesegment comprises less than about 5 percent by weight of celluloseacetate, preferably less than 3 percent by weight of cellulose acetate,more preferably less than 1 percent by weight of cellulose acetate, evenmore preferably less than 0.1 percent by weight cellulose acetate. Thismay favourable further contribute to enhance biodegradability of thehollow tube segment and of the aerosol-generating article as a whole.

Preferably, an aerosol-generating article in accordance with the presentinvention comprises less than or equal to about 10 percent by weight ofcellulose acetate measured with reference to the overall weight of theaerosol-generating article. More preferably, an aerosol-generatingarticle in accordance with the present invention comprises less than orequal to about 7 percent by weight of cellulose acetate measured withreference to the overall weight of the aerosol-generating article. Evenmore preferably, an aerosol-generating article in accordance with thepresent invention comprises less than or equal to about 5 percent byweight of cellulose acetate measured with reference to the overallweight of the aerosol-generating article. This advantageously indicatesthat not only the hollow tube segment has a low or null content ofcellulose acetate, but also that any other component of the articlecontaining a fibrous filtration material contains little to no celluloseacetate. Embodiments of aerosol-generating articles in accordance withthe invention having such low contents of cellulose acetate presentparticularly favourable biodegradability properties.

In some preferred embodiments, an aerosol-generating article inaccordance with the present invention comprises less than or equal toabout 3 percent by weight of cellulose acetate measured with referenceto the overall weight of the aerosol-generating article. Morepreferably, an aerosol-generating article in accordance with the presentinvention comprises less than or equal to about 2 percent by weight ofcellulose acetate measured with reference to the overall weight of theaerosol-generating article. Even more preferably, an aerosol-generatingarticle in accordance with the present invention comprises less than orequal to about 1 percent by weight of cellulose acetate measured withreference to the overall weight of the aerosol-generating article.

In some highly preferred embodiments, an aerosol-generating article inaccordance with the present invention is substantially free of celluloseacetate.

In some embodiments, the fibrous filtration material further comprisesat least one biodegradable polymer selected from the group consisting ofstarch, polybutylene succinate (PBS), polybutyrate adipate terephthalate(PBAT), thermoplastic starch and thermoplastic starch blends (TPS),polycaprolactone (PCL), polyglycolide (PGA), polyvinyl alcohol(PVOH/PVA), viscose, regenerated cellulose, polysaccharides, celluloseacetate with a degree of substitution (DS) of less than 2.1, polyamides,protein-based biopolymers, chitosan-chitin based biopolymers, andcombinations thereof.

The inventors have found that including one or more of these ingredientsin the blend from which the fibrous material of the filter segment isformed further contributes to enhancing biodegradability of the filtersegment and of the aerosol-generating article as a whole.

In addition, while it has previously been found to be technicallychallenging to manufacture PHA-containing filaments or fibres, usingexisting techniques and apparatus, the inventors have surprisingly foundthat it is possible to produce a filaments or fibres incorporating ahigh level of PHAs when the PHAs are combined in a blend as describedabove, as this makes it easier to form the filaments by a spinningtechnique.

In some embodiments, the fibrous filtration material comprises at leastabout 5 percent by weight of one such additional biodegradable polymer.In preferred embodiments, the fibrous filtration material comprises atleast about 10 percent by weight of one such additional biodegradablepolymer. More preferably, the fibrous filtration material comprises atleast about 11 percent by weight or at least 12 percent by weight or atleast 13 percent by weight or at least 14 percent by weight of theadditional biodegradable polymer. Even more preferably, the fibrousfiltration material comprises at least about 15 percent by weight of onesuch additional biodegradable polymer.

In particularly preferred embodiments, the at least one biodegradablepolymer is one or more of PBAT, PCL and PBS. Without wishing to be boundby theory, the inventors have found that use of one or more of theseselected biodegradable polymers contributes to improving the mechanical,thermal and morphological properties of the polymer mix. In particular,use of PBAT and PBS in combination has been found to provide especiallywell balanced mechanical properties, especially in terms of tensilestrength and elongation.

In some embodiments, the fibrous filtration material comprises at leastabout 3 percent by weight of a plasticiser selected from triacetin,triethylene glycol diacetate (TEGDA), ethylene vinyl acetate, polyvinylalcohol, starch or combinations thereof.

In some embodiments, the fibrous filtration material also furthercomprises a water based adhesive. This has the effect of structurallyreinforcing the structure of the hollow tube segment. By way of example,compounds such as starch adhesive, methyl cellulose or polyvinyl acetatemay be used to this purpose.

Preferably, the fibrous filtration material of the hollow tube segmentcomprises a plurality of fibres comprising a PHA polymer or copolymerand having a denier per filament of at least about 1. More preferably,the fibrous filtration material of the hollow tube segment comprises aplurality of fibres comprising a PHA polymer or copolymer and having adenier per filament of at least about 2. Even more preferably, thefibrous filtration material of the hollow tube segment comprises aplurality of fibres comprising a PHA polymer or copolymer and having adenier per filament of at least about 3.2.

In preferred embodiments, the fibrous filtration material of the hollowtube segment comprises a plurality of fibres comprising a PHA polymer orcopolymer and having a denier per filament of less than or equal toabout 10. More preferably, the fibrous filtration material of the hollowtube segment comprises a plurality of fibres comprising a PHA polymer orcopolymer and having a denier per filament of less than or equal toabout 7.5. Even more preferably, the fibrous filtration material of thehollow tube segment comprises a plurality of fibres comprising a PHApolymer or copolymer and having a denier per filament of less than orequal to about 5.

In some embodiments, the fibrous filtration material of the hollow tubesegment comprises a plurality of fibres comprising a PHA polymer orcopolymer and having a denier per filament of from about 1 to about 10,more preferably from about 2 to about 10, even more preferably fromabout 3.2 to about 10. In other embodiments, the fibrous filtrationmaterial of the hollow tube segment comprises a plurality of fibrescomprising a PHA polymer or copolymer and having a denier per filamentof from about 1 to about 7.5, more preferably from about 2 to about 7.5,even more preferably from about 3.2 to about 7.5. In furtherembodiments, the fibrous filtration material of the hollow tube segmentcomprises a plurality of fibres comprising a PHA polymer or copolymerand having a denier per filament of from about 1 to about 5, morepreferably from about 2 to about 5, even more preferably from about 3.2to about 5.

Without wishing to be bound by theory, the inventors have found thatwhen the hollow tube segment is formed from PHA fibres having arelatively low dpf of between 1.5 and 3.2, the hollow tube segmentexhibits a particularly low RTD, which may be desirable for the designof certain aerosol-generating articles. One such low range of dpf alsoadvantageously reduces the overall weight of the hollow tube segment,which further significantly improves the biodegradability of theaerosol-generating article.

Preferably, the fibres comprising a PHA polymer or copolymer of thefilter segment are crimped.

The transverse cross-sectional shape of the PHA fibres may be varied,for example, in order to control the external surface area of the fibreswithin the hollow tube segment. By controlling the external surface areaof the PHA fibres, the total surface area of the PHA fibres that isexposed to the aerosol as it passes through the hollow tube segment mayalso be controlled. This in turn will control to some extent thefiltration properties of the PHA fibres, for example, the amount ofwater that is adsorbed by the fibres in conventional combustible smokingarticles.

In some embodiments, the PHA fibres have a substantially roundcross-section. In such embodiments, the total external surface area ofthe PHA fibres within the hollow tube segment is preferably betweenabout 0.15 square metres per gram and about 0.30 square metres per gram.

In alternative embodiments, the PHA fibres have a Y-shapedcross-section. In such embodiments, the total external surface are ofthe PHA fibres within the hollow tube segment is preferably betweenabout 0.15 square metres per gram and about 0.55 square metres per gram.More preferably, the total external surface are of the PHA fibres withinthe hollow tube segment is between about 0.2 square metres per gram andabout 0.5 square metres per gram, even more preferably between about0.25 square metres per gram and about 0.45 square metres per gram.

In some embodiments, the hollow tube segment may comprise one or moreadditive for reducing certain constituents in the mainstream smoke. Byway of example, the filter segment preferably comprises an additive forthe reduction of phenols and phenol derivatives. [ . . . ]

The combination of PHA with an additive such as PEG for the reduction ofphenolic compounds from the mainstream smoke has been found to beparticularly effective. PHA fibres generally provide a good filtrationefficiency for undesirable smoke constituents but are less effective atthe removal of phenolic compounds. By incorporating a compound thatspecifically reduces the level of phenolic compounds in the mainstreamsmoke, it is possible to further optimise the filtration capabilities ofthe hollow tube segment of an aerosol-generating article in accordancewith the invention, in particular when a hollow tube segment asdescribed above is used as a component of a multi-component filter in acombustible smoking article, such as a filter cigarette. This in turnimproves the sensory characteristics of the aerosol delivered to theconsumer.

In particularly preferred embodiments, the hollow tube segment furthercomprises at least about 5 percent by weight of polyethylene glycol,based on the total weight of the filtration material. Preferably, thehollow tube segment comprises no more than 10 percent by weight ofpolyethylene glycol, based on the total weight of the filtrationmaterial.

As described above, it has been found that PHA fibres absorb less waterfrom the mainstream smoke than an equivalent amount of cellulose acetatefibres, due to the lower affinity of the PHA fibres to water. Asdemonstrated in the examples below, the amount of water absorbed by aPHA filter segment is significantly lower than the amount of waterabsorbed by a comparative filter segment formed of an equivalent weightof cellulose acetate fibres.

For example, when exposed to water in liquid form, the hollow tubesegment of the aerosol-generating article of the present inventionpreferably absorbs less than half the amount of water that is absorbedunder the same conditions by an equivalent hollow tube segment formed ofcellulose acetate fibres.

The reduced absorption of water by the PHA fibres in the hollow tubesegment of the present invention, compared to cellulose acetate resultsin a higher level of water in the mainstream smoke delivered from theaerosol-generating article during use.

For example, the amount of water in the mainstream smoke collectedduring the smoking of a combustible smoking article comprising a filteraccording to the invention with PHA fibres under ISO conditions was atleast 10 percent higher and preferably at least 15 percent higher thanthe amount of water in the mainstream smoke collected during the smokingof an equivalent combustible smoking article having a filter segment ofcellulose acetate tow under the same conditions.

Aerosol-generating articles comprising a filter including a PHA hollowtube segment are therefore able to deliver a mainstream smoke having ahigher moisture level, which is more sensorially acceptable to theconsumer. In particular, the ‘dry smoke’ effect that may be experiencedduring smoking of an aerosol-generating article with a conventionalcellulose acetate filter can advantageously be reduced.

The fibres comprising a PHA polymer or copolymer of the filter segmentmay be manufactured by one of several techniques, including meltspinning, gel spinning, and electrospinning. Preferably, the fibrescomprising a PHA polymer or copolymer of the filter segment inaerosol-generating articles in accordance with the present invention aremanufactured by melt spinning. Melt spinning is often regarded as themost economical process of spinning, since no solvent needs to berecovered or evaporated, as is by contrast the case with solutionspinning. Further, the spinning rate with melt spinning is generallyfairly high, which is advantageous in terms of overall productivity andmanufacturing efficiency.

In this process, a viscous melt of polymer or of a polymer blend isextruded through a spinneret containing a number of holes into achamber, where a blast of cold air or gas is directed onto the surfaceof filaments emanating from the spinneret. As the air strikes thefilaments, the filaments are solidified and collected such as on atake-up wheel. The melt spinning process is advantageously characterisedby defined filament cross-section geometries and affords a significantvariety of fineness and filament count. By increasing the number ofopenings in the spinneret, a high spinning capacity can be achieved,which is difficult to match with other spinning processes.

Preferably, in an aerosol-generating article in accordance with thepresent invention the hollow tube segment does not substantiallycontribute to an overall RTD of the aerosol-generating article.

Thus, in aerosol-generating articles in accordance with the presentinvention the overall RTD of the article preferably depends essentiallyon the RTD of the rod and may further depend on the RTD of optionaladditional components, such as a mouthpiece or a filter segment, as asignificant proportion of the overall volume of the hollow tube segmentis substantially empty and, as such, the hollow tube segment onlymarginally contributes to the overall RTD.

In practice, the hollow tube segment may be adapted to generate a RTD inthe range of approximately 0 millimetre H₂O (about 00 Pa) toapproximately 20 millimetres H₂O (about 200 Pa). Preferably, the hollowtube segment is adapted to generate a RTD between approximately 0millimetres H₂O (about 00 Pa) to approximately 10 millimetres H₂O (about100 Pa).

The aerosol-generating article preferably has an overall RTD of lessthan about 90 millimetres H₂O (about 900 Pa). More preferably, theaerosol-generating article has an overall RTD of less than about 80millimetres H₂O (about 800 Pa). Even more preferably, theaerosol-generating article has an overall RTD of less than about 70millimetres H₂O (about 700 Pa).

Preferably, the aerosol-generating article has an overall RTD of atleast about 30 millimetres H₂O (about 300 Pa). More preferably theaerosol-generating article has an overall RTD of at least about 40millimetres H₂O (about 400 Pa). Even more preferably, theaerosol-generating article has an overall RTD of at least about 50millimetres H₂O (about 500 Pa).

In some embodiments, the aerosol-generating article has an overall RTDfrom about 30 millimetres H₂O (about 300 Pa) to about 90 millimetres H₂O(about 900 Pa), preferably from about 40 millimetres H₂O (about 400 Pa)to about 90 millimetres H₂O (about 900 Pa), more preferably from about50 millimetres H₂O (about 500 Pa) to about 90 millimetres H₂O (about 900Pa). In other embodiments, the aerosol-generating article has an overallRTD from about 30 millimetres H₂O (about 300 Pa) to about 80 millimetresH₂O (about 800 Pa), preferably from about 40 millimetres H₂O (about 400Pa) to about 80 millimetres H₂O (about 800 Pa), more preferably fromabout 50 millimetres H₂O (about 500 Pa) to about 80 millimetres H₂O(about 800 Pa). In further embodiments, the aerosol-generating articlehas an overall RTD from about 30 millimetres H₂O (about 300 Pa) to about70 millimetres H₂O (about 700 Pa), preferably from about 40 millimetresH₂O (about 400 Pa) to about 70 millimetres H₂O (about 700 Pa), morepreferably from about 50 millimetres H₂O (about 500 Pa) to about 70millimetres H₂O (about 700 Pa).

The RTD of the aerosol-generating article may be assessed as thenegative pressure that has to be applied, under test conditions asdefined in ISO 3402, to downstream end of the article in order tosustain a steady volumetric flow of air of 17.5 ml/s through thearticle. The values of RTD listed above are intended to be measured onthe aerosol-generating article on its own (that is, without insertingthe article into an aerosol-generating device) and, if a ventilationzone if provided in the article, without blocking any perforations ofthe ventilation zone.

In other embodiments, the aerosol-generating article has an overall RTDof at least about 150 millimetres H₂O (about 1500 Pa), preferably atleast about 200 millimetres H₂O (about 2000 Pa), more preferably atleast about 250 millimetres H₂O (about 2500 Pa).

The hollow tube segment comprising PHA fibres in accordance with thepresent invention has additionally been found to provide a goodstability in the RTD, which means that a high variability in the RTD canadvantageously be avoided. For example, within a sample of 20 of theaerosol-generating articles according to the invention, there willtypically be a standard deviation from the target RTD of between 2percent and 10 percent, more preferably between 2 percent and 5 percent.

The hollow tube segment preferably has a wall thickness of at leastabout 0.3 millimetres. More preferably, the hollow tube segment has awall thickness of at least about 0.4 millimetres. Even more preferably,the hollow tube segment has a wall thickness of at least about 0.5millimetres.

Preferably, the hollow tube segment has a wall thickness of less than orequal to about 1.9 millimetres. More preferably, the hollow tube segmenthas a wall thickness of less than or equal to about 1.5 millimetres.Even more preferably, the hollow tube segment has a wall thickness ofless than or equal to about 1.2 millimetres. Particularly preferably,the hollow tube segment has a wall thickness of less than or equal toabout 0.9 millimetres.

In certain embodiments, the hollow tube segment has a wall thicknessfrom about 0.3 millimetres to about 1.9 millimetres, preferably fromabout 0.4 millimetres to about 1.9 millimetres, more preferably fromabout 0.5 millimetres to about 1.9 millimetres. In some embodiments, thehollow tube segment has a wall thickness from about 0.3 millimetres toabout 1.5 millimetres, preferably from about 0.4 millimetres to about1.5 millimetres, more preferably from about 0.5 millimetres to about 1.5millimetres. In other embodiments, the hollow tube segment has a wallthickness from about 0.3 millimetres to about 1.2 millimetres,preferably from about 0.4 millimetres to about 1.2 millimetres, morepreferably from about 0.5 millimetres to about 1.2 millimetres. Infurther embodiments, the hollow tube segment has a wall thickness fromabout 0.3 millimetres to about 0.9 millimetres, preferably from about0.4 millimetres to about 0.9 millimetres, more preferably from about 0.5millimetres to about 0.9 millimetres. In a particularly preferred,exemplary embodiment, the hollow tube segment has a wall thickness ofabout 0.6 millimetres.

In some embodiments, the hollow tube segment may typically have a lengthof at least about 4 millimetres. Preferably, a length of the hollow tubesegment is at least about 5 millimetres. More preferably, a length ofthe hollow tube segment is at least about 7 millimetres. Even morepreferably, a length of the hollow tube segment is at least about 10millimetres.

In certain embodiments, a length of the hollow tube segment is less thanor equal to about 35 millimetres. Preferably, a length of the hollowtube segment is less than or equal to about 25 millimetres. Morepreferably, a length of the hollow tube segment is less than or equal toabout 20 millimetres. Even more preferably, a length of the hollow tubesegment is less than or equal to about 15 millimetres.

In preferred embodiments, a length of the hollow tube segment is fromabout 4 millimetres to about 35 millimetres. Preferably, a length of thehollow tube segment is from about 5 millimetres to about 35 millimetres.More preferably, a length of the hollow tube segment is from about 7millimetres to about 35 millimetres. Even more preferably, a length ofthe hollow tube segment is from about 10 millimetres to about 35millimetres.

In certain other embodiments, a length of the hollow tube segment isfrom about 4 millimetres to about 25 millimetres. Preferably, a lengthof the hollow tube segment is from about 5 millimetres to about 25millimetres. More preferably, a length of the hollow tube segment isfrom about 7 millimetres to about 25 millimetres. Even more preferably,a length of the hollow tube segment is from about 10 millimetres toabout 25 millimetres.

In other embodiments, a length of the hollow tube segment is from about4 millimetres to about 20 millimetres. Preferably, a length of thehollow tube segment is from about 5 millimetres to about 20 millimetres.More preferably, a length of the hollow tube segment is from about 7millimetres to about 20 millimetres. Even more preferably, a length ofthe hollow tube segment is from about 10 millimetres to about 20millimetres.

In further embodiments, a length of the hollow tube segment is fromabout 4 millimetres to about 15 millimetres. Preferably, a length of thehollow tube segment is from about 5 millimetres to about 15 millimetres.More preferably, a length of the hollow tube segment is from about 7millimetres to about 15 millimetres. Even more preferably, a length ofthe hollow tube segment is from about 10 millimetres to about 15millimetres.

Preferably, in aerosol-generating articles in accordance with thepresent invention the hollow tube segment has an average radial hardnessof at least about 80 percent, more preferably at least about 85 percent,even more preferably at least about 90 percent. The hollow tube segmentis therefore able to provide a desirable level of hardness to theaerosol-generating article, which is comparable to that provided by aconventional cellulose acetate hollow tube segment.

If desired, the radial hardness of the hollow tube segment ofaerosol-generating articles in accordance with the invention may befurther increased by circumscribing the hollow tube segment by a stiffplug wrap, for example, a plug wrap having a basis weight of at leastabout 80 grams per square metre (gsm), or at least about 100 gsm, or atleast about 110 gsm.

As used herein, the term “radial hardness” refers to resistance tocompression in a direction transverse to a longitudinal axis of thehollow tube segment. Radial hardness of an aerosol-generating articlearound a hollow tube segment may be determined by applying a load acrossthe article at the location of the hollow tube segment, transverse tothe longitudinal axis of the article, and measuring the average (mean)depressed diameters of the articles. Radial hardness is given by:

${{Radial}{hardness}(\%)} = {\frac{D_{d}}{D_{S}}*100\%}$

where D_(S) is the original (undepressed) diameter, and D_(d) is thedepressed diameter after applying a set load for a set duration. Theharder the material, the closer the hardness is to 100%.

To determine the hardness of a portion (such as a hollow tube segment)of an aerosol article, aerosol-generating articles should be alignedparallel in a plane and the same portion of each aerosol-generatingarticle to be tested should be subjected to a set load for a setduration. This test is performed using a known DD60A Densimeter device(manufactured and made commercially available by Heinr Borgwaldt GmbH,Germany), which is fitted with a measuring head for aerosol-generatingarticles, such as cigarettes, and with an aerosol-generating articlereceptacle.

The load is applied using two load-applying cylindrical rods, whichextend across the diameter of all of the aerosol-generating articles atonce. According to the standard test method for this instrument, thetest should be performed such that twenty contact points occur betweenthe aerosol-generating articles and the load applying cylindrical rods.In some cases, the hollow tube segments to be tested may be long enoughsuch that only ten aerosol-generating articles are needed to form twentycontact points, with each smoking article contacting both load applyingrods (because they are long enough to extend between the rods). In othercases, if the hollow tube segments are too short to achieve this, thentwenty aerosol-generating articles should be used to form the twentycontact points, with each aerosol-generating article contacting only oneof the load applying rods, as further discussed below.

Two further stationary cylindrical rods are located underneath theaerosol-generating articles, to support the aerosol-generating articlesand counteract the load applied by each of the load applying cylindricalrods.

For the standard operating procedure for such an apparatus, an overallload of 2 kg is applied for a duration of 20 seconds. After 20 secondshave elapsed (and with the load still being applied to the smokingarticles), the depression in the load applying cylindrical rods isdetermined, and then used to calculate the hardness from the aboveequation. The temperature is kept in the region of 22 degreesCentigrade±2 degrees. The test described above is referred to as theDD60A Test. The standard way to measure the filter hardness is when theaerosol-generating article have not been consumed. Additionalinformation regarding measurement of average radial hardness can befound in, for example, U.S. Published Patent Application PublicationNumber 2016/0128378.

An aerosol-generating article in accordance with the present inventionmay comprise one or more further components that may be assembled withthe rod of aerosol-generating substrate and with the hollow tube segmentin a same wrapper.

Examples of such additional elements include a mouthpiece filtrationsegment, a cooling element adapted to favour cooling of the aerosolprior to reaching the mouthpiece, and so forth.

By way of example, the mouthpiece may comprise a filter segment, that isa plug of filtration material. The mouthpiece may, in particular,comprise a plug of a fibrous filtration material. Suitable filtrationmaterials are known in the art and include, but are not limited to:fibrous filtration materials such as, for example, cellulose acetatetow, viscose fibres, polylactic acid (PLA) fibres and paper; adsorbentssuch as, for example, activated alumina, zeolites, molecular sieves andsilica gel; and combinations thereof.

In some preferred embodiment, the fibrous filtration material used forforming the mouthpiece may be the same fibrous filtration materialcontaining a PHA-containing polymer or copolymer described above for thehollow tube segment of the present invention. This may be particularlyadvantageous, as the desirable effects associated with a fibrousfiltration material comprising a PHA-containing polymer or copolymer interms of biodegradability and water-absorption properties extend also tothe mouthpiece plug. As such, an aerosol-generating article may beprovided that has especially advantageous properties.

In addition, the filter segment of the mouthpiece may further compriseone or more aerosol-modifying agent. Suitable aerosol-modifying agentsare known in the art and include, but are not limited to, flavourantssuch as, for example, menthol.

In some embodiments, the hollow tube segment may be used at thedownstream end of the aerosol-generating article, in axial alignmentwith the mouthpiece filter segment, preferably immediately adjacent to adownstream end of the mouthpiece filter segment. In such embodiments,the hollow tube segment defines a mouth end recess downstream of theplug of filtration material. Thus, the hollow tube segment forms acavity at the mouth end that is open to the outer environment at thedownstream end of aerosol-generating article.

In such embodiments, the filter segment of the mouthpiece may typicallyhave a length of less than or equal to about 30 millimetres. Preferably,a length of the filter segment is less than or equal to about 27millimetres. More preferably, a length of the filter segment is lessthan or equal to about 25 millimetres. Even more preferably a length ofthe filter segment it less than or equal to about 20 millimetres.

In such embodiments, a length of the filter segment is preferably fromabout 5 millimetres to about 30 millimetres, more preferably from about10 millimetres to about 30 millimetres, even more preferably from about15 millimetres to about 30 millimetres, most preferably from about 20millimetres to about 30 millimetres. Alternatively, in such embodimentsa length of the filter segment may be from about 4 millimetres to about27 millimetres, and preferably is from about 5 millimetres to about 27millimetres, more preferably from about 10 millimetres to about 27millimetres, even more preferably from about 15 millimetres to about 27millimetres, most preferably from about 20 millimetres to about 27millimetres. As a further alternative, in such embodiments, a length ofthe filter segment may be from about 4 millimetres to about 25millimetres, and preferably is from about 5 millimetres to about 25millimetres, more preferably from about 10 millimetres to about 25millimetres, even more preferably from about 15 millimetres to about 30millimetres, most preferably from about 20 millimetres to about 25millimetres.

The filter segment preferably has an external diameter that is aboutequal to the external diameter of the aerosol-generating article.Preferably, the filter segment has an external diameter of at least 5millimetres. The filter segment may have an external diameter of betweenabout 5 millimetres and about 12 millimetres, for example of betweenabout 5 millimetres and about 10 millimetres or of between about 6millimetres and about 8 millimetres. In a preferred embodiment, thefilter segment has an external diameter of 7.2 millimetres, to within 10percent.

In some embodiments, the mouthpiece comprises a single filter segment asdescribed above. In other embodiments, the aerosol-generating articlemay comprise one or more additional filter segments. In some preferredembodiments, each one of the filter segments of the mouthpiececomprising a PHA polymer or copolymer as described above.

As an alternative, a filter segment comprising a PHA polymer orcopolymer may be combined with one or more axially aligned filter plugsformed of a fibrous filtration material not including PHA-containingfibres. Alternatively or in addition, a filter segment comprising a PHApolymer or copolymer may be combined with a tubular element formed of acardboard tube.

The mouthpiece filter segment of aerosol-generating articles accordingto the invention may optionally comprise a flavourant. Flavourants canbe incorporated using a variety of different means, which would be knownto the skilled person. For example, a flavourant may be incorporated inthe form of a capsule which may be provided in a filter segmentcomprising a PHA polymer or copolymer.

For example, in one preferred embodiment, an aerosol-generating articlecomprises, in linear sequential arrangement, a first plug of filtrationmaterial, a rod of aerosol-generating substrate located immediatelydownstream of the first plug of filtration material, a hollow tubesegment as described above with a support function located immediatelydownstream of the rod, a second plug of filtration material locateddownstream of the hollow tube segment, and an outer wrappercircumscribing the first plug, the rod, the support element, and thesecond plug.

The invention will now be further described with reference to thefigures in which:

FIG. 1 shows a schematic longitudinal cross-sectional view of anaerosol-generating article according to a first embodiment of theinvention, for use with an aerosol-generating device comprising a heaterelement;

FIG. 2 shows a schematic longitudinal cross-sectional view of anaerosol-generating article according to a second embodiment of theinvention, comprising an integral heat source;

FIG. 3 shows a schematic longitudinal cross-sectional view of anaerosol-generating article according to a third embodiment of theinvention; and

FIG. 4 shows a schematic longitudinal cross-sectional view of anaerosol-generating system comprising an electrically operatedaerosol-generating device and the aerosol-generating article shown inFIG. 1 .

The aerosol-generating article 10 shown in FIG. 1 comprises a rod ofaerosol-generating substrate 12, a support element provided as a hollowtubular element 14, a cooling element 16, and a mouth end filter segment18. These four elements are arranged sequentially and in coaxialalignment and are circumscribed by a substrate wrapper 20 to form theaerosol-generating article 10. The aerosol-generating article 10 has amouth end 22 and a distal end 24 located at the opposite end of thearticle to the mouth end 22. The aerosol-generating article 10 shown inFIG. 1 is particularly suitable for use with an electrically operatedaerosol-generating device comprising a heater for heating the rod ofaerosol-generating substrate.

In use air is drawn through the aerosol-generating article by a userfrom the distal end 24 to the mouth end 22. The distal end 24 of theaerosol-generating article may also be described as the upstream end ofthe aerosol-generating article 10 and the mouth end 22 of theaerosol-generating article 10 may also be described as the downstreamend of the aerosol-generating article 10. Elements of theaerosol-generating article 10 located between the mouth end 22 and thedistal end 24 can be described as being upstream of the mouth end 22 or,alternatively, downstream of the distal end 24.

The aerosol-generating substrate 12 is located at the extreme distal orupstream end of the aerosol-generating article 10. In the embodimentillustrated in FIG. 1 , the aerosol-generating substrate 12 comprises agathered sheet of crimped homogenised tobacco material circumscribed bya wrapper. The crimped sheet of homogenised tobacco material comprisesglycerin as an aerosol former.

The support element 14 is located immediately downstream of theaerosol-generating substrate 12 and abuts the aerosol-generatingsubstrate 12. In the embodiment shown in FIG. 1 , the support element isa hollow tube formed of a fibrous filtration material. The supportelement 14 locates the aerosol-generating substrate 12 at the extremedistal end 24 of the aerosol-generating article 10 so that it can bepenetrated by a heating element of an aerosol-generating device. Ineffect, the support element 14 acts to prevent the aerosol-generatingsubstrate 16 from being forced downstream within the aerosol-generatingarticle 10 towards the aerosol-cooling element 16 when a heating elementof an aerosol-generating device is inserted into the aerosol-generatingsubstrate 12. The support element 14 also acts as a spacer to space theaerosol-cooling element 16 of the aerosol-generating article 10 from theaerosol-generating substrate 12.

The aerosol-cooling element 16 is located immediately downstream of thesupport element 14 and abuts the support element 14. In use, volatilesubstances released from the aerosol-generating substrate 12 pass alongthe aerosol-cooling element 16 towards the mouth end 22 of theaerosol-generating article 10. The volatile substances may cool withinthe aerosol-cooling element 16 to form an aerosol that is inhaled by theuser. In the embodiment illustrated in FIG. 1 , the aerosol-coolingelement comprises a tubular element 20. The crimped and gathered sheetof polylactic acid defines a plurality of longitudinal channels thatextend along the length of the aerosol-cooling element 40.

The filter segment 18 is located immediately downstream of theaerosol-cooling element 16 and abuts the aerosol-cooling element 16.

In the embodiment illustrated in FIG. 1 , the filter segment 18comprises a single cylindrical plug of a fibrous filtration materialformed of a plurality of PHA fibres having a denier per filament ofapproximately 3 and a total denier of approximately 27,000. The PHAfibres have a round cross-sectional shape and are substantiallylongitudinally aligned with each other along the length of the filtersegment. The exposed surface area of the PHA fibres corresponds to about0.16 square metres per gram. The PHA fibres have been formed by a meltspinning process and are crimped. The plug of fibrous filtrationmaterial is circumscribed by a plug wrap (not shown).

Further, the support element 14 is a hollow tube segment comprisingfibrous filtration material formed of a plurality of PHA fibres having adenier per filament of approximately 3 and a total denier ofapproximately 27,000. The PHA fibres have a round cross-sectional shapeand are substantially longitudinally aligned with each other along thelength of the filter segment. The exposed surface area of the PHA fibrescorresponds to about 0.16 square metres per gram. The PHA fibres havebeen formed by a melt spinning process and are crimped. In more detail,the fibres contain about 85 percent by weight of a PHA polymer orcopolymer combined with 15 percent by weight of a of PBAT/PBS blend witha 1:1 PBAT to PBS ratio.

The aerosol-generating article 100 shown in FIG. 2 comprises acombustible heat source 112, a rod of aerosol-generating substrate 114,a transfer element 116, an aerosol-cooling element, 118, a spacerelement 120 and a mouthpiece filter segment 122. These elements arearranged sequentially and in coaxial alignment and are circumscribed bya substrate wrapper to form the aerosol-generating article 100.

The combustible heat source 112 comprises a substantially circularlycylindrical body of carbonaceous material, having a length of about 10millimetres. The combustible heat source 112 is a blind heat source. Inother words, the combustible heat source 112 does not comprise any airchannels extending therethrough.

The rod of aerosol-generating substrate 114 is arranged at a proximalend of the combustible heat source 112. The aerosol-generating substrate114 comprises a substantially circularly cylindrical plug of tobaccomaterial 124 circumscribed by filter plug wrap 126.

A non-combustible, substantially air impermeable first barrier 128 isarranged between the proximal end of the combustible heat source 112 anda distal end of the aerosol-generating substrate 114. The first barrier128 comprises a disc of aluminium foil. The first barrier 128 also formsa heat-conducting member between the combustible heat source 112 and theaerosol-generating substrate 114, for conducting heat from the proximalface of the combustible heat source 112 to the distal face of theaerosol-generating substrate 114.

A heat-conducting element 130 circumscribes a proximal portion of thecombustible heat source 112 and a distal portion of the aerosol-formingsubstrate 114. The heat-conducting element 130 comprises a tube ofaluminium foil. The heat-conducting element 130 is in direct contactwith the proximal portion of the combustible heat source 112 and thefilter plug wrap 126 of the aerosol-generating substrate 114.

The mouthpiece filter 122 comprises a single cylindrical plug 126 of afibrous filtration material formed of a plurality of PHA fibres having adenier per filament of approximately 3 and a total denier ofapproximately 27,000. The PHA fibres have a round cross-sectional shapeand are substantially longitudinally aligned with each other along thelength of the filter segment. The exposed surface area of the PHA fibrescorresponds to about 0.16 square metres per gram. The PHA fibres havebeen formed by a melt spinning process and are crimped. The plug offibrous filtration material is circumscribed by a plug wrap (not shown).

The spacer element 120 is provided as a hollow tube segment inaccordance with the present invention and comprises comprising fibrousfiltration material formed of a plurality of PHA fibres having a denierper filament of approximately 3 and a total denier of approximately27,000. The PHA fibres have a round cross-sectional shape and aresubstantially longitudinally aligned with each other along the length ofthe filter segment. The exposed surface area of the PHA fibrescorresponds to about 0.16 square metres per gram. The PHA fibres havebeen formed by a melt spinning process and are crimped. In more detail,the hollow tube segment has an inner diameter of about 3.30 millimetresand an outer diameter of about 7.10 millimetres, which corresponds to awall thickness of about 1.90 millimetres.

The aerosol-generating article 310 shown in FIG. 3 is a combustiblesmoking article comprising an aerosol-generating substrate 312 and afilter 314 arranged in coaxial alignment with each other. Theaerosol-generating substrate 312 comprises a tobacco rod circumscribedby an outer wrapper (not shown). A tipping wrapper 316 circumscribesboth the filter 314 and an end portion of the aerosol-generatingsubstrate 312 and attaches the filter 314 to the aerosol-generatingsubstrate 312.

The filter 314 comprises a cylindrical plug 318 of a fibrous filtrationmaterial formed of PHA fibres having a denier per filament ofapproximately 3 and a total denier of approximately 27,000. The PHAfibres have a round cross-sectional shape and are substantiallylongitudinally aligned with each other along the length of the filtersegment. The exposed surface area of the PHA fibres corresponds to about0.16 square metres per gram. The PHA fibres have been formed by a meltspinning process and are crimped. The plug of fibrous filtrationmaterial is circumscribed by a plug wrap (not shown).

In addition, the filter 314 comprises a hollow tube segment 320 arrangedin axial alignment with the plug 318 and immediately downstream of theplug 318. The hollow tube segment 320 comprises a fibrous filtrationmaterial formed of PHA fibres having a denier per filament ofapproximately 3 and a total denier of approximately 27,000. The PHAfibres have a round cross-sectional shape and are substantiallylongitudinally aligned with each other along the length of the filtersegment. The exposed surface area of the PHA fibres corresponds to about0.16 square metres per gram. The PHA fibres have been formed by a meltspinning process and are crimped.

FIG. 4 shows a portion of an electrically operated aerosol-generatingsystem 200 that utilises a heater blade 210 to heat the rod ofaerosol-generating substrate 12 of the aerosol-generating article 10shown in FIG. 1 . The heater blade 210 is mounted within anaerosol-generating article chamber within a housing of an electricallyoperated aerosol-generating device 212. The aerosol-generating device212 defines a plurality of air holes 214 for allowing air to flow to theaerosol-generating article 10, as illustrated by the arrows in FIG. 4 .The aerosol-generating device 212 comprises a power supply andelectronics, which are not shown in FIG. 4 .

Comparative Example

[Incorporate Discussion of Tests 1 and 2 from IDR?]

A PHA filter segment according to the invention is prepared from PHAfibres, with the parameters shown in Table 1 below. The PHA fibres areformed using a melt spinning process, the fibres are then crimped andformed into a filter segment using standard filter making apparatus. Forthe purposes of comparison, a conventional cellulose acetate (CA) towfilter segment is prepared, with similar values of denier per filament(dpf) and total denier.

TABLE 1 parameters of PHA filter segment and cellulose acetate filtersegment Parameter PHA filter segment CA filter segment Denier perfilament 3.2 3 Total denier 27000 27000 Weight in filter segment (mg)406.76 409.76 Exposed surface area (m²/g) 0.161 0.329

In a first test, the water absorption by exposure to water of the PHAfilter segment according to the invention and the CA filter segment arecompared. For each filter segment, the plug wrap is removed and thefilter segment is attached to the probe of a force tensiometer (KRUSSforce tensiometer, Model K100). The filter segment is moved down by theprobe towards a container of water and automatically stopped when thefilter segment makes contact with the water. The filter segment isretained in contact with the water for 300 seconds so that the filtermaterial can absorb water and then the filter segment is weighed inorder to determine the amount of water absorbed during the test period.For each of the PHA filter segment and the CA filter segment, this testis repeated three times and an average value of water absorption wascalculated, as shown below in Table 2:

TABLE 2 Water absorption of the PHA and CA filter segments afterexposure to water PHA filter segment CA filter segment Water absorptionin 300 0.51 1.37 sec (g)

The amount of water absorbed by the PHA filter segment according to theinvention during the test was therefore less than 40 percent of theamount of water absorbed by the CA filter segment. This test thereforedemonstrates the significantly reduced affinity of water of the PHAfilter segment according to the invention compared to the conventionalCA filter segment.

In a second test, the water absorption by exposure to moisture of thePHA filter segment according to the invention and the CA filter segmentare compared. For each filter segment, the plug wrap is removed and thefibres forming the filter segment are placed in a petri dish and exposedto air at 22 degrees Celsius and 50 percent relative humidity for 70hours. This is conducted in a vapour sorption analyser (ProUmidSPSx-1μ). For each filter segment, the weight of the fibres is measuredat the start of the test and the change in weight over time due to theabsorption of water vapour by the fibres is measured. For each of thePHA filter segment and the CA filter segment, a value of the percentagedifference in mass of the sample (% dm) is calculated, which expressesthe increase in the weight of the sample as a percentage of the originalweight. The values of % dm for each of the samples at the end of the 70hour test are shown below in Table 3:

TABLE 3 Water absorption of the PHA and CA filter segments afterexposure to moisture PHA filter segment CA filter segment % Differencein mass after 0.0133 0.6784 70 hours (% dm)

The results demonstrate that the amount of water vapour absorbed by thecellulose acetate fibres during the 70 hour test was more than 50 timesgreater than the amount of water vapour absorbed by the PHA fibres. ThePHA fibres absorbed very little water vapour during the test. Thisfurther demonstrates the significantly reduced affinity of water of thePHA filter segment according to the invention compared to theconventional CA filter segment.

In a third test, the absorption of water from the mainstream smoke by aPHA filter segment according to the present invention and a conventionalCA filter segment are compared. For each of the filter segments, aconventional smoking article is prepared as described above withreference to FIG. 3 , with a combustible tobacco rod and a singlesegment of the filtration material forming the filter. Each of thesmoking articles is then smoked in a cigarette-smoking machine under ISOconditions as set out in ISO 3308:2000 (puff volume 35 ml; 2 second puffduration every 60 seconds) and an analysis of the resultant smoke iscarried out.

For each of the filter segments, the amount of water in the mainstreamsmoke collected during the smoking test is measured, as shown in Table4:

TABLE 4 Water in mainstream smoke generated during smoking test underISO conditions PHA filter segment CA filter segment Water (mg persmoking 0.82 0.68 article)

This demonstrates that when smoked under equivalent conditions, thesmoking article incorporating the PHA filter segment produces amainstream smoke having a water content that is approximately 20 percenthigher than the water content of the mainstream smoke from the smokingarticle including the CA filter segment. This demonstrates that the PHAfilter segment is absorbing less water from the mainstream smoke thanthe CA filter segment, thereby reducing the potential problem of drysmoke as described above.

1.-15. (canceled)
 16. An aerosol-generating article for producing aninhalable aerosol upon heating, the aerosol-generating articlecomprising: a rod of aerosol-generating substrate, theaerosol-generating substrate comprising at least 12 percent by weight ofan aerosol former, and the rod having a length of from 5 millimetres to50 millimetres; and a hollow tube segment with a support element andcomprising fibrous filtration material, the hollow tube segment disposedimmediately downstream of the rod and in longitudinal alignment with therod, wherein the fibrous filtration material comprises fibres comprisinga polyhydroxyalkanoate (PHA) polymer or copolymer, and wherein thehollow tube segment comprises at least about 25 percent by weight of thePHA polymer or copolymer.
 17. The aerosol-generating article accordingto claim 16, wherein the fibrous filtration material further comprisesat least about 85 percent by weight of fibres comprising thepolyhydroxyalkanoate (PHA) polymer or copolymer.
 18. Theaerosol-generating article according to claim 16, wherein the fibrousfiltration material further comprises at least about 90 percent byweight of fibres comprising the polyhydroxyalkanoate (PHA) polymer orcopolymer.
 19. The aerosol-generating article according to claim 16,wherein the fibrous filtration material further comprises at least about5 percent of fibres comprising cellulose acetate.
 20. Theaerosol-generating article according to claim 19, wherein the fibrousfiltration material further comprises at least about 10 percent offibres comprising cellulose acetate.
 21. The aerosol-generating articleaccording to claim 16, wherein the fibres comprising thepolyhydroxyalkanoate (PHA) polymer or copolymer further comprise atleast one biodegradable polymer selected from the group consisting ofstarch, polybutylene succinate (PBS), polybutyrate adipate terephthalate(PBAT), thermoplastic starch and thermoplastic starch blends (TPS),polycaprolactone (PCL), polyglycolide (PGA), polyvinyl alcohol(PVOH/PVA), viscose, regenerated cellulose, polysaccharides, celluloseacetate with a degree of substitution (DS) of less than 2.1, polyamides,protein-based biopolymers, chitosan-chitin based biopolymers, andcombinations thereof.
 22. The aerosol-generating article according toclaim 21, wherein the at least one biodegradable polymer is one or moreof PBAT, PCL, and PBS.
 23. The aerosol-generating article according toclaim 16, wherein the fibrous filtration material further comprises atleast about 3 percent by weight of a plasticiser selected fromtriacetin, triethylene glycol diacetate (TEGDA), ethylene vinyl acetate,polyvinyl alcohol, starch, or combinations thereof.
 24. Theaerosol-generating article according to claim 16, wherein the fibrescomprising the polyhydroxyalkanoate (PHA) polymer or copolymer havebetween 3.2 denier per filament and 5 denier per filament.
 25. Theaerosol-generating article according to claim 16, wherein the fibrescomprising the polyhydroxyalkanoate (PHA) polymer or copolymer arecrimped.
 26. The aerosol-generating article according to claim 16,wherein a resistance to draw (RTD) of the hollow tube segment is lessthan about 10 millimetres H₂O.
 27. The aerosol-generating articleaccording to claim 16, wherein the hollow tube segment has a wallthickness of at least about 0.3 millimetres, or a wall thickness of lessthan or equal to about 1.5 millimetres, or both.
 28. Theaerosol-generating article according to claim 16, wherein the hollowtube segment has a length of at least about 4 millimetres.
 29. Theaerosol-generating article according to claim 16, wherein a dry radialhardness of the hollow tube segment is at least about 90 percent.
 30. Asystem comprising an aerosol-generating device and an aerosol-generatingarticle according to claim 16 for the aerosol-generating device, theaerosol-generating device being configured to heat rather than combustthe aerosol-generating substrate.